Model Accuracy

Lightpoint recently completed an extensive investigation to quantify the accuracy of our methodology, and the results have recently been accepted for publication by SAE for 2016. The complete abstract is below, but in short, we modeled three vehicles of varying size (a minivan, sedan, and hatchback) via photogrammetry and compared those results to measurements obtained via total station (2 mm accuracy), and a FARO Arm (0.124 mm accuracy).

The results of the study are shown in the table below. Notice, the average residual between corresponding photogrammetry and total station measurements was only 1.7 mm (N = 258), which is below the accuracy range of the total station (2 mm). For the corresponding FARO measurements, the average residual dropped to 1.2 mm (N = 83).

Again, the study will be published by SAE in 2016. The full abstract is below:

Three targeted vehicles of varying size were measured using an optimized, practical photogrammetry technique and the results were compared to measurements acquired via total station. The photogrammetry method included the use of a field-calibrated DSLR camera equipped with a fixed 20mm lens, retroreflective targets sized for vehicular modeling, and a CNC-machined scale bar. Eight photographs were taken from proper angles and processed using a commercially available photogrammetry package. This data was merged with the total station data using a cloud-to-cloud registration process for point-to-point comparison of positional data. The average residual between corresponding photogrammetry and total station points was 1.7 mm (N = 258, SD = 0.8 mm) with a 95% confidence limit of 3.1 mm. Considering this low residual, one of the sample vehicles was re-measured using a high accuracy FARO Arm for comparison to the photogrammetry technique. The average residual between corresponding photogrammetry and FARO Arm points was 1.2 mm (N = 83, SD = 0.56 mm) with a 95% confidence limit of 2.1 mm. This research shows photogrammetry can be highly accurate and efficient with proper methodology, while also expanding on the photogrammetry literature database and improving confidence in the technique.